Preparation of diols containing an adamantane nucleus



United States Patent 3,383,424 PREPARATION OF DKOLS CONTAINING ANADAMANTANE NUCLEUS Robert E. Moore, Wilmington, Del., assignor to SunOil glompany, Philadelphia, Pin, a corporation of New ersey No Drawing.Continuation-impart of application Ser. No. 421,614, Dec. 28, 1964. Thisapplication Aug. 30, 1967, Ser. No. 664,311

12 Claims. (Cl. 266--617) ABSTRACT OF THE DISCLGSURE Preparation of1,3-cliols of adamantane or C; C alkyladarnantanes by contacting theparent hydrocarbon with an acetic acid solution of chromic acid inamount such that the Cr to hydrocarbon molar ratio is in excess' of 3:1.

Cross reference to related application This application is acontinuation of application Ser. No. 421,614, filed Dec. 28, 1964, nowabandoned.

Background of the invention This invention relates to the preparation ofdiols rom adamantane or from alkyladarnantanes having from eleven toeighteen carbon atoms and at least two unsubstituted bridgeheadpositions. More specifically the invention involves the oxidation ofthese adamantane hydrocarbons by means of chromic acid under certainconditions resulting in the formation of two hydroxy groups attached tothe adamantane nucleus at bridgehead positions.

The carbon nucleus of adamantane (tricyclo[3.3.l.1 decane) contains tencarbon atoms arranged in a completely symmetrical, strainless mannersuch that four of the carbon atoms occupy bridgehead positions in therings. The structure of adamantane is often depicted typographically asfollows:

C HO CH H CH2 Description of the invention It has now been found thatdiols of adamantane and C C alkyladamantanes can be produced by chromicacid oxidation of the hydrocarbon provided that certain conditions areused in the reaction. These conditions include the use of aqueous aceticacid as solvent for the chromic acid and the use of chromic acid inamount such that the atoms of Cr per molecule of hydrocarbon are atleast 3 :1 and more preferably in excess of 5:1. The aqueous acetic acidshould have an acetic content or strength in the range of 7095% byweight, more preferably 70-85%. By utilizing high ratios ofCrzhydrocarbon as above specified the diol can be formed in high yieldwith essentially no monool being in the reaction product.

3,383,424 Patented May 14, 1968 ice The acetic acid content as hereinexpressed refers to the strength that the acetic acid would have if itand water were the only constituents present. Expressed another way, theweight ratio of acetic acid to water in the re action mixture should bein the range of 95:5 to :30, and it preferably does not exceed 85: 15.

In one manner of carrying out the oxidation the chromic acid solution isfirst prepared by dissolving chromium trioxide in the aqueous aceticacid or by dissolving it in Water and then adding an amount of aceticacid to the solution to reach an acetic acid strength in the range of70-95% by Weight. The concentration of chromic acid in the solution isnot critical but typically may be in the range of 2030% by weight. Theadamantane hydrocarbon is then introduced into the reagent solution inwhich it is essentially insoluble, and the mixture is agitated wherebyan exothermic reaction occurs. The amount of hydrocarbon so added issuch that the Crzhydrocarbon molar ratio is at least 3:1 and preferablyis in excess of 5: 1, i.e., at least 3 and more preferably 5 atoms ofchromium are present per molecule of the adamantane hydrocarbon. Thereaction can be effected by agitating the mixture at any temperature inthe range of 10- 250 C. However the minimum molar ratio of Cr to totaladamantane hydrocarbon added that is suitable for obtaining a good yieldof diol varies somewhat depending upon the initial temperature at whichthe hydrocarbon and oxidant are contacted. More specifically theCrzhydrocarbon molar ratios as a minimum should be approximately asfollows:

(1) At least 4:1 when the initial contacting temperature is in the rangeof 10-40 C.

(2) At least 3.5:1 when the initial contacting temperature is in therange of 4060 C. p

(3) At least 3:1 when the initial contacting temperature is above 60 C.Preferably the reaction is started at a temperature within the range of60120 C. and is held in such temperature range to obtain a relativelyfast reaction rate while avoiding sludge formation which tends to occurat higher temperatures.

The oxidation reaction is exothermic, and as the reaction proceeds themixture generally will become homogeneous. The reaction is continueduntil at least a major portion and preferably all of the hydrocarbon hasbeen oxidized. This will result in the formation of two hydroxyl groupsper molecule which groups will be located at bridgehead positions of theadamantane nucleus. When the Crzhydrocarbon ratio is 5:1 or higherlittle if any monool will be present in the reaction product when thereaction is completed. The time of reaction of course will depend uponthe particular reaction temperature selected but typically may be of theorder of 2-5 hours at C.

After the oxidation is complete, the reaction mixture can be chilled bymeans of ice and a portion of the diol product will precipitate fromsolution and can be separated by filtration. Neutralization of thefiltrate with ammonium hydroxide will then cause most of the diolproduct to precipitate, and the diol thus obtained again can beseparated by filtration. Some of the diol will re main in solutionbecause of its solubility in water, and it can be recovered by lettingthe mixture evaporate to near dryness. In some cases the product maycontain small amounts of a hydroxyketo derivative and a mono-ester ofacetic acid.

The chromic acid for effecting the oxidation can also be prepared froman alkali metal dichromate, such as Na Cr O or K Cr O and sulfuric acid.A substantial molar excess of H 50 relative to the dichromate saltshould be employed and preferably the molar ratio of 3 H SO to Na Cr O(or K Cr O should exceed 2:1. High ratios of these components tend toincrease the yield of dihydroxyadamantane compound produced in thereaction.

Regardless of whether the chromic acid is formed from CrO or from thealkali metal dichromates, the presence of acetic acid in the reactionmixture in large amount relative to the adamantane hydrocarbon is highlydesirable. The molar ratio of these two components generally should beat least 10:1 and more preferably should exceed :1. These ratios arebased upon the equivalent amount of glacial acetic acid (i.e., CH COOH).If the acetic acid is omitted from the reaction mixture, the reactionproduct will be predominantly the rnonohydroxyadamantane derivative andonly small amounts (e.g., 5%) of the diol will be produced.

In some instances in practicing the invention the reaction product maycomprise both the monohydroxy and dihydroxy derivatives in substantialamounts. For obtaining the 1,3-diol in high purity and high yield theproduct mixture can be treated with pentane, petroleum ether oranhydrous ethyl ether. Any of these solvents or equivalent solvents willselectively dissolve the monool and other oxidation products and leavethe diol as residue. A suitable procedure is to mix the reactionproducts with boiling solvent, cool the mixture to room temperature,filter and then wash the residue with an additional amount of solvent.The filtrate generally will have a greenish color while the diol residuewill be white crystals. The monool can be obtained in the form of whitecrystals from the filtrate by cooling the latter to dry ice temperatureand filtering.

The following are some specific adamantane hydrocarbone which can beconverted to diols according to the invention:

adamantane; l-methyladamantane; l-ethyladamantane;1,3-dimethyladamantane; 1-methyl-3-ethyladamantane;2-methyl-4-ethyladamantane; 1,3,6-trimethyladamantane;1,3-dipropyladamantane; l-hexyladamantane; l-octyladamantane; and thelike.

The following examples illustrate the invention:

Examples I-V In order to illustrate the importance of the ratio of Cratoms to molecules of starting hydrocarbon as herein specified, a seriesof runs was made in which 1,3-dimethyladamantane (DMA) was oxidizedusing various Crzhydrocarbon ratios. Each run was carried out in astirred reactor using aqueous acetic acid containing 85% by weight ofacetic acid and chromium trioxide (CrO as the source of chromic acid. Ineach case the reaction was started at about room temperature by addingthe hydrocarbon dropwise, whereupon the temperature rose in about 15minutes to within the range of 75-90 C. where it was maintained forabout 3.3 hours. The molar ratio of acetic acid to total DMA added wasabout 22:1. The products were recovered from the reaction mixtures byprecipitation and filtration in the manner previously described. Theywere analyzed by vapor phase chromatography in conjunction with infraredspectra and the results are shown in Table I.

TABLE I.OXIDATION OF DIME'IHYLADAMANTANE Run No 1 2 3 4 5 Mole Ratio ofCr: DMA 1. 5 3. 34 4 5 6 Product composition, wt. perre 4 From the datain Table I it can be seen that the Cr: hydrocarbon ratio used has amarked effect on the composition of the reaction product. At relativelylow ratios the main reaction product is the bridgehead monoalcohollisted as l-rnonool. Since the reaction was started at room temperaturerather than at a higher temperature level, it was only after the CrzDMAratio had been increased to above 4:1 that the principal reactionproduct was the bridgehead diol. The data show that at ratios above 5:1the 1,3-dihydroxydimethyladamantane is obtained in surprisingly highpurity even when the reaction is started at room temperature. This diolproduct is a crystalline solid having a melting point of about 2l.4215C.

Example VI Another run (No. 6) was made in which l-ethyladamantane wasoxidized using a 5:1 molar ratio of Crzhydrocarbon and a 22:1 molarratio of acetic acid to the ethyladamantane. Again the chromic acid wasderived from chromic trioxide, aqueous acetic acid was used, thereaction was begun at room temperature and was allowed to rise to 75-90C., and the temperature then was maintained in this range for about 3.3hours. Analysis of the reaction product showed the following compositionby weight:

TABLE II.--OXIDATIO.N OF ETHYLADAMANTANES Percent1,3-dihydroxy-S-ethyladamantane 97.5 Ketoalcohol 1.5 Unknown 1.0

After further purification of the diol by recrystallization fromacetone, it was found to have a melting point of C.

Examples VII1X Three runs were made in which the charge hydrocarbon was1,3-dimethyladarnantane (DMA) and the combination of sodium dichromateand sulfuric acid was used to form the chromic acid. In all three runs10.0 g. (0.061. mole) of the dimethyladamantane and 36.1 g. (0.122 mole)of Na2Cr2072H2O were used. This corresponded to 4.0 atoms of chromiumper molecule of the hydrocarbon. In Run 7 no acetic acid was presentwhere relatively large amounts were used in Runs 8 and 9. In each runthe reaction was started at room temperature by adding the DMA dropwisewhereupon the temperature rose to 7590 C. in about 15 minutes. While themixture was being stirred, the temperature was then maintained at thislevel for about 3.3 hours. The reaction products were recovered in thesame manner as in the preceding examples. Analyses of the products byvapor phase chromatography gave the results shown in Table III. Thechromatograph column used detected only the monoalcohol and dialcohol asreaction products, but it is probable that small amounts of otherreaction products as shown in Table I were present. Table III shows thecomposiiton of the reaction mixtures and of the products for Runs 7-9.

Reaction mixture composition, moles:

1,3-dimethy1adarnantane 0. 61 0. 061 O. 061 Acetlc acid 1. 35 1. 21H1804 0.156 0. 306 Water 0. 84 0. 88 NaaCrzO7-2H2O 0.122 0.122 Weightratio of acetic acid to wat 84:16 82 18 Molar ratio of acetic acid toDMA 22 1 20:1 Reaction product, wt. percent:

l-monool 68 30 1,3-diol 32 70 Comparison of Run 7 with Runs 8 and 9shows the importance of having acetic acid in the reaction mixture inrelatively large amount in order to produce the diol. When no aceticacid was used, the product was mainly the monoalcohol. A comparison ofRuns 8 and 9 shows that to obtain a good yield of the diol a substantialmolar excess of sulfuric acid relative to the dich'romate should beemployed. In Run 8 the molar ratio of these two components was 1.28 andthe proportion of diol in the product was only 32%; whereas in Run 9where the ratio was 2.5 the diol content increased to 70%. To obtain astill better yield of diol, the amounts of the dichromate and sulfuricacid relative to the hydrocarbon should be increased.

Examples X-XIII Four more runs were made for oxidizing1,3-dimethyladamantane (DMA) in generally the same manner as in ExamplesI-V using CrO as the source of chromic acid. However, in these runs theaqueous acetic acid solution of chromic acid was heated to 7590 C. andthen the addition of DMA was begun while the mixture was being stirred.The time of addition of the DMA was about 45 minutes and the reactiontime from the start of such addition was about 3.5 hours. The Cr:DMAratios were as listed in Table IV and otherwise the conditions were asdescribed for Examples I-V. Results from vapor phase chromatography aregiven in Table IV.

A comparison of these results with those of Table I shows the efiect ofstarting the reaction at elevated tern perature instead of at roomtemperature. As can be seen from Table IV, when the chromic acidsolution was heated to 75-90 C. before addition of the hydrocarbon, aCrzDMA ratio of 3:1 was sufficient to result in formation of the diol asthe major product. On the other hand as shown in Table I, when thehydrocarbon Was first added at room temperature and the temperature wassubsequently maintained at 7590 C. after it had risen to that level,even a Cr:D MA ratio of 4:1 was not quite suflicient to cause the diolto be the major product although it was produced in substantial yield.Both tables show that Cr:hydrocarbon molar ratios above 5:1 arepreferable 'for producing the 1,3-diol in high purity.

When adamantane or any C C alkyladamantane having at least twounsubstituted bridgehead positions is substituted for the hydrocarbonsused in the foregoing examples, substantially similar results areobtained. When the reaction is attempted omitting the acetic acid andusing only an aqueous solution of chromic acid, no reaction occurs.

The 1,3-diols prepared in accordance with the invention are useful asintermediates in the preparation of special lubricants and polymers. Forexample, the diols can be reacted with aliphatic monocarboxylic acids(e.g., pelargonic acid to produce ester lubricants as described inapplication Ser. No. 531,059, filed Mar. 2, 1966. Also they can beinteracted with various diacids, anhydrides or diacid chlorides to yieldhigh molecular weight polyesters as disclosed in application Ser. No.586,825, filed Oct. 14, 1966, or with dinitriles to form high molecularWeight polyamides as described in application Ser. No. 542,229, filedApr. 13, 1966.

I claim:

1. Method of forming -a diol having an adamantane nucleus whichcomprises contacting chromic acid in an aqueous solution of acetic acidhaving an acetic acid strength in the range of 95% at a temperature inthe range of 10-250 C. with an adamantane hydrocarbon selected from thegroup consisting of adamantane and alkyladamantanes having .l118 carbonatoms and at least two unsubstituted bridge-head positions, theCr:hydr-ocarbon molar ratio being at least 4:1 when the initialcontacting temperature is in the range of 1040 C., at least 3.5:1 whenit is the range of 40-60 C. and at least 3:1 when it is above 60 C.,whereby an exothermic oxidation reaction occurs, continuing the reactionuntil at least a major portion of said hydrocarbon has reacted, andrecovering from the reaction mixture an adamantane diol having thehydroxyl substituents at bridgehead positions.

2. Method according to claim 1 wherein said temperature is in the rangeof 60- C.

3. Method according to claim 2 wherein the strength of said aqueoussolution of acetic acid is 70-85%.

4. Method according to claim 1 wherein said hydrocarbon is1,3-dimethyladamant'aue.

5. Method according to claim 1 wherein said hydrocarbon isl-ethyladamantane.

6. Method according to claim 1 wherein the Crzhydrocarbon molar ratio isat least 5:1.

7. Method according to claim 6 wherein the molar ratio of acetic acid tosaid adamantane hydrocarbon is in excess of 15:1.

8. Method according to claim 1 wherein the molar ratio of acetic acid tosaid adamantane hydrocarbon is at least 10:1.

9. Method of forming a diol of an adamant-ane hydrocarbon selected fromthe group consisting of adamantane and alkyladamantanes having 11-18carbon atoms and at least two unsubstituted bridgehead positions whichcomprises forming a mixture of chromic acid in aqueous acetic acidhaving an acetic acid strength in the range of 7095%, maintaining saidmixture at a temperature in the range of 60l20 C. while adding theretoand mixing therewith an amount of said adamantane hydrocarbon such thatthe molar ratio of Cr to total added adamantane hydrocarbon is in excessof 32-1, whereby an exothermic oxidation reaction occurs, continuing thereaction until at least a major portion of said hydrocarbon has reacted,and recovering from the reaction mixture an adamantane diol having thehydroxyl substituents at bridgehead positions.

10. Method according to claim 9 wherein said molar ratio is in excess of5: 1.

11. Method according to claim 10 wherein the molar ratio of acetic acidto said adamantane hydrocarbon is in excess of 15:1.

12. Method according to claim 9 wherein the molar ratio of acetic acidto said adamantane hydrocarbon is at least 10:1.

References Cited Schleyer et al.: I. Am. Chem. Soc., vol. 83, pp. 182- 7(1961).

Stetter et al.: Chem. Abstracts, vol. 54, p. 20,9l2e (1960).

BERNARD HELFIN, Acting Primary Examiner. T. G. DILLAHU'NTY, AssistantExaminer.

